The invention relates to an applicator for semi-solid materials, sometimes called “stick products,” including but not limited to lip balm (such as shown in U.S. Pat. No. 7,695,727 and the prior art discussed therein), sunscreen, skin balm, analgesic balm, lipstick, deodorant, and make-up. The applicator according to the invention is simple and easy to use, simple and inexpensive to manufacture, versatile, and aesthetic. The applicator is also easily refillable and therefore more environmentally sound than other tangentially related products such as shown in U.S. Pat. Nos. 5,799,667, 6,193,427, and 8,444,337, and is expected to have a long shelf life. The applicator is also easy to use to effectively apply stick products to a human's body, including lips, underarms, or other portions of skin.
According to one aspect of the invention, a stick product semi-solid material applicator is provided which comprises: A generally tubular housing having first and second open ends. An elastomeric material base cap closing the housing first end. A plunger having first and second ends, the plunger first end operatively connected to the flexible material cap. A mass of semi-solid material stick product mounted on the second end of the plunger. And, at least one readily removable end cap covering the housing second end. The end cap is movable from a first position in which it covers the semi-solid material to preclude access thereto, and a second position in which the semi-solid material can extend at least partially out the housing second end.
The elastomeric material base cap may be concave in relaxed position so as to bias the semi-solid material to the second position extending at least partially out of the second end of the housing. Preferably, however, the elastomeric material base cap is a bistable element which moves from a first stable configuration in which the semi-solid material is primarily within the housing to, after removal of the end cap and manual actuation thereof, a second stable configuration in which the semi-solid mass is substantially completely exterior of the housing. The base cap may be of urethane or a similar thermoplastic material, and desirably has a durometer of about 40-90 (e. g. about 70) on the Shore A scale.
The applicator also desirably includes at least one stop in the interior of the housing between the first and second ends thereof for stopping the movement of the plunger at a desired position. Also, the at least one end cap preferably comprises a mold for the semi-solid material to allow in situ molding thereof on the plunger. Compatible projections are provided on the housing adjacent the second end thereof, and on the end cap, to provide releasable locking connection of the end cap to the housing.
Desirably, the plunger comprises a shaft and a tray which holds the semi-solid material, the tray having a peripheral section devoid of semi-solid material; and wherein the end cap can engage the peripheral section to move the semi-solid material from the second position to the first position thereof without adversely affecting the semi-solid material. The plunger also may comprise a disc (integral with or detached from the shaft) adjacent the second end of the shaft which cooperates with the tray to minimize contact of the semi-solid material with air inside the housing. The plunger shaft and tray may have cooperating surface manifestations to allow releasable connection of one to the other, or may be integral. The plunger also has a knob and recess at the first end thereof which cooperates with surface manifestations on the elastomeric material base cap to allow ready replacement of the plunger and semi-solid material mass.
Preferably, a guide is provided mounted within the housing between the first and second ends thereof which guides reciprocal movement of the plunger. The guide cooperates with vertical ribs on the plunger that define a diameter or other cross-sectional dimension that is the same as, or slightly greater than, the diameter or other cross-sectional dimension of the plunger knob.
The generally tubular housing can have a wide variety of different shapes including a uniform diameter circle in cross-section, a uniform or tapered polygon (e. g. hexagon) in cross-section, or it may have tapering side walls at least one of which is substantially flat.
According to another aspect of the invention there is provided a method of assembling an applicator unit with a semi-solid stick product, the applicator unit including a plunger shaft, a plunger tray having openings and surface manifestations (such as tabs) therein, and an end cap having an open top and a bottom in the form of a mold. The method is characterized by: a) Placing the tray on the open top of the end cap. b) Filling the bottom of the end cap with flowable stick product so that it passes through the openings in the plunger tray and engages the surface manifestations. c) Allowing the flowable stick product to cool or otherwise set into a semi-solid mass attached to the plunger tray but not attached to the end cap bottom. And d) ensuring that the plunger shaft is in operative association with the plunger tray so that the tray and semi-solid mass move with the plunger shaft.
The method is desirably for use with a generally tubular applicator housing having a bistable elastomeric material base cap, and is further characterized by: e) Moving an end of the plunger shaft opposite the tray into contact with the elastomeric material base cap so that they are releasably connected together. f) Pushing the end cap into operative association with surface manifestations on the end of the housing opposite the base cap so that they releasable lock together. And g) removing the end cap and acting on the bistable base cap so that the base cap biases the semi-solid mass of stick product out of the housing for use on a user's body.
According to yet another aspect of the present invention there is provided an applicator, comprising: A bistable body of elastomeric material having a peripheral portion with inner and outer surfaces, and a center portion with top and bottom surfaces, the center portion top surface having a convex shape in a first relaxed configuration, and a concave shape in a second relaxed configuration, and the center portion bottom surface having a depending center tubular element. Surface manifestations in the interior of the center tubular element for cooperation with a knob and recess of a plunger. And surface manifestations on the inner surface of the peripheral portion for cooperation with a housing for an applicator. The cap is desirably made of a thermoplastic material with properties comparable to those of urethane and has a durometer of between about 40-90 (e. g. about 70) on the Shore A scale.
It is the primary object of the present invention to provide a particularly desirable applicator for stick products, such as lip balm, a novel base cap for the applicator, and a method of assembly and utilization of the applicator. This and other objects of the invention will become clear from a detailed description of the drawings, and from the appended claims.